There is general consensus among the major automakers that hydrogen-powered fuel cells will be the power source of future cars and trucks. But there is also agreement that it won't happen anytime soon.

Hydrogen-powered fuel cells are pollution-free power plants whose only emission is water vapor. How long before we see such cars arrive in the marketplace? American Honda Motor Company's manager of alternative fuels, Gunnar Lindstrom, answers. "We are a long, long way from there. Let me preface this by saying, it may be twenty years before we see fuel cell cars in any meaningful numbers," he says.

Another leader in fuel cell research, General Motors, is more optimistic. The Director of Business Development for GM Fuel Cell Activities, Tim Vail, says their target date is 2010. As to the reasons why fuel cells remain on the far horizon? Tim Vail says "the technology, cost and infrastructure are the three big obstacles - and technology and cost are combined. As we come up with new technologies and remove componentry out of the existing technology platform, the cost is reduced. And we feel we have a good "handle" on driving down that cost and we'll be able to get there by our 2010 target."

Automakers are generally looking at two approaches to hydrogen as a fuel - as a liquid or a gas. In its gaseous form, says Honda's Gunnar Lindstrom, an issue is "filling up" the tank under pressure. "That has to be standardized so we can all use the same refueling station, or at least it requires special systems if the fueling stations are going to dispense different pressures. Currently, our vehicles are at 5,000 pounds (per square inch). That works very well. Other automakers have suggested going to 10,000 pounds, and that works very well also, but of course you'd have to spend quite a bit of energy to compress the fuel from 5,000 to 10,000," he says.

Liquid hydrogen presents its own problems, being "cryogenic", or super-cold. GM's Tim Vail says there may be another solution. "We think in the future, there'll be a hybrid-type technology between liquid and compressed [gas]," he says. "And that's what we're working on actively, to come up with some new solutions."

Setting up a fueling infrastructure for hydrogen will be a huge task. But Mr. Vail says it's definitely do-able. "To get adequate coverage, so that you could fill up a hydrogen-fueled vehicle, like for example, in a major city - a gas station every two miles - the numbers aren't that great. We're really looking in the range of about 10,000 gas stations which, at today's technology, is about a $10 to $11 billion issue. Indeed, a lot of money, but certainly not something that's going to break the bank," he says.

Gunnar Lindstrom of Honda sees two ways of handling the infrastructure challenge. "Either you can transport fuel, ready to use, through pipelines or tankers or any other way. Or you can actually manufacture fuel on-site, where you will use it and by-pass the whole idea of hydrogen pipelines, for example," he says.

Then there are the vehicles themselves. Honda's Gunnar Lindstrom says they must be at least as good as today's cars in performance, reliability, ease-of-use and price. "We have to build cars that people actually want to buy and drive, you know, needless to say. And, with a fuel cell car, even though we have production cars that are running right now, they do not meet those criteria," he says.

And, until they do, hydrogen-powered fuel cell cars will remain a good idea whose time is not yet here.